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Datang Dolun Coal-to-Olefins Project’s Unit Achieves Another Record for Continuous Stable Operation Author/Source: Huahua Network – Coal Chemicals Date: 2020-06-15 Clicks: 8 On May 31, Unit 4 in the power center of Datang Dolun’s coal-to-polypropylene project achieved 220 days of continuous stable operation, setting a new record for the longest operating period since the unit was put into use. As of June 4, all five boilers in the power plant were operating stably at high load. The 5 420 t/h boilers in Dolun Company’s power plant were manufactured by Sichuan Zigong Huaxi Energy Industry Co., Ltd., and are designed to use lignite as fuel. Lignite is characterized by high moisture, high volatile matter, high ash content, low ash fusion point, and low calorific value. For the design of the lignite boiler, a volumetric heat load of 92.44 kW/m3 and a cross-sectional heat load of 3033 kW/m2 were selected. With such a design, under the same evaporation rate, a higher heat input is required from the boiler. Since the boiler was put into operation, tube failures have occurred frequently on its heating surfaces due to factors such as soot blowing and flue gas erosion, forcing the boiler to shut down; this has also become a bottleneck affecting its long-term operation. Faced with difficult circumstances, the staff and workers at the power center did not wait or rely on others; instead, they faced the challenges head-on and, with the courage to make tough decisions, fought desperately to seize every moment in this critical struggle. Through active exploration and evidence-based treatment, every effort is made to resolve the issue of frequent boiler tube failures. First, the Power Center established a task force dedicated to developing technologies for preventing wear and explosions in boilers, with the manager of the Power Center serving as its leader and members from the boiler management team forming part of this group. Adhering to a work style characterized by rigor, attention to detail, and practicality, they devoted themselves wholeheartedly to carrying out inspections aimed at preventing wear and explosions. From the economizer to the low-temperature superheater, and from the high-temperature superheater to the screen superheater, every row of pipes and every area prone to damage is carefully inspected and marked, leaving no corner unexamined. For each boiler, the principle of \"conducting inspections whenever it stops operating, performing trend analysis, and implementing proactive control\" is always adhered to in order to carry out inspections aimed at preventing wear and explosions on the boiler’s heating surfaces. The patterns of wear on these \"four types of tubes\" are monitored, and corresponding measures are developed to ensure that their protection against wear and explosions is effectively managed, thus guaranteeing the boiler’s stable, continuous, and optimal operation. Secondly, by reviewing past records of boiler tube failures, it was found that multiple instances of such failures were caused by damage resulting from soot blowing. After extensive research, the boiler specialists in the process team switched from automated soot blowing to manual, selective soot blowing, based on the degree of contamination of each boiler’s heating surfaces. The soot blowing pressure was reduced from 2.1 MPa to 1.7 MPa, and the frequency of soot blowing was decreased from 3 times per day to 1.5 times per day, thereby reducing the wear on the heating surfaces caused by soot blowing. At the same time, a specialized comprehensive inspection team was established to focus on checking the operating condition of the soot blowers, ensuring that each cleaning process is thorough and effective. This reduces the likelihood of damage to the heating surfaces and prevents boiler tube failures caused by the failure to deactivate the soot blowers in a timely manner. At the same time, the boiler team adjusts the operating pressure of the coal grinder and the angle of the separation baffles in accordance with the quality of the coal fed into the boiler, thereby ensuring the fineness of the coal powder at the grinder’s outlet, reducing the amount of primary air used, and minimizing mechanical wear on the heating surfaces. Next, the power center will modify the boiler by raising the feedwater temperature and optimizing the layout of the convective heating surfaces, in order to improve the reliability of boiler operation as well as its efficiency. One direction, two sets of solutions – multiple measures taken to ensure the long-term stable operation of the equipment. “One direction” refers to the overall goal of maintaining stable production levels and ensuring continuous operational capacity throughout the year; “two sets of solutions” refer to the plans for dealing with minor equipment failures without having to shut down the equipment, as well as emergency procedures to be followed during periods when shutdown is not possible. This general direction serves as the goal for every worker in this field, while the “two sets of procedures” represent the standard approaches to dealing with emergency situations. No detail is overlooked in these procedures, and the correct steps to follow have long been firmly ingrained in the minds of each operator. Some of the equipment in the power center is operating beyond its capacity, and some equipment is showing signs of wear and age; therefore, it is necessary for team members to conduct inspections in order to identify these problems. Inspection work is the most direct and effective method for all chemical plants to check whether equipment is operating properly, and this is true as well for power centers. On many occasions, it has been through the stethoscopes, flashlights in the hands of inspectors, along with their responsible attitude, that various potential problems have been identified. According to statistics, in 2019 inspection workers identified over 900 potential hazards. The timely identification of these hazards ensured their rapid removal, which is essential for the continuous and stable operation of the equipment. To help someone make greater progress, the way is undoubtedly to strengthen their learning and to engage in practical work on the front line. Every year, when new trainees arrive at the Power Center, in addition to mentorship programs and regular examinations, the center also arranges for them to go to the actual sites as soon as possible. There, they are given detailed explanations regarding furnace temperature, the ratio of coal used in combustion, reaction rates, etc. Each trainee is required to act as a teacher in turn, giving lectures; through repeated explanations, the trainees can develop rapidly. Those with strong comprehension skills and a willingness to put in effort are identified for focused training, in order to build a pool of talent for the Power Center. The Datang Duolun Coal Chemical Project uses lignite from the Shengli Coal Field in Xilinhot City, Inner Mongolia, as raw material. It employs Shell’s powder gasification technology, Hangyang’s air separation process with internal compression, low-temperature methanol washing, Lurgi’s low-pressure methanol synthesis method, and Lurgi’s MTP process for propylene production. Dow Chemical’s UNIPOL process is also used for propylene polymerization. The project has an annual production capacity of 1.68 million tons of methanol as an intermediate product; ultimately, it produces 460,000 tons of polypropylene, along with 240,000 tons of high-purity methanol, 129,500 tons of gasoline, and 66,600 tons of LPG.